|Rank|City|Population|Area (km2)|Density (inhabitants/km2)|Altitude (mslm)|
|---|---|---|---|---|---|
|1st|Alessandria|94191|203.97|461.8|95|
|2nd|Casale Monferrato|36039|86.32|417.5|116|
|3rd|Novi Ligure|28581|54.22|527.1|197|
|4th|Tortona|27476|99.29|276.7|122|
|5th|Acqui Terme|20426|33.42|611.2|156|
|6th|Valenza|20282|50.05|405.2|125|
|7th|Ovada|11912|35.33|337.2|186|
|8th|Serravalle Scrivia|6445|16.02|402.3|225|
|9th|Arquata Scrivia|6260|30.36|206.2|248|
|10th|Castelnuovo Scrivia|5473|45.42|120.5|85|

Question: how many cities have at least 25,000 people?
Answer: 4